Add three environment variables for deployments with external identity
providers (Keycloak, Authentik, Ory Hydra, etc.):
- OAUTH_EXTRA_SCOPES: append additional scopes to the default
"openid email profile" (e.g. "offline_access" for refresh tokens)
- OAUTH_SCOPES: full override of the requested OAuth scopes
- COOKIE_SECURE: override the Secure flag on auth cookies (useful
for reverse proxy setups where the internal hop is HTTP)
Without these, deploying Bulwark with an external OIDC provider that
requires `offline_access` for refresh tokens is impossible — sessions
die on every page refresh because no refresh token is issued.
All three are backwards-compatible: unset = identical to current behavior.
